NO - Besoin d'assistance

Composition of tomatoes and tomato products in antioxidants (WG1) page 43
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(between 0.06 and 0.45 Mpa) of the nutrient solutions depending on either Cl - or/and NO3 - . In
a study of the effect of 4 irrigation regimes (40, 50, 60 and 70% depletion of available soil
moisture) on tomato cultivars Pusa Ruby, Pusa Early Dwarf and Sioux, Naphade (1993)
observed that ascorbic acid content in tomato fruit increased as moisture stress increased,
together with total soluble solids, acidity, sugars, sugar:acid ratio, and percentage of cracked
fruits. The 60% depletion regime produced also fruits of good size and the highest water use
efficiency. However Zushi et Matsuzoe (1998) reported that the effects of soil water deficit on
vitamin C content (fresh matter basis) varied, depending on the cultivar; in some cultivars
vitamin C content increased, whereas in others it was unaffected. In tomato plants of two
cultivars (Matador and Elin) grown in rockwool slabs under greenhouse, Petersen et al.(1998)
showed that increased salinity (3 to 9 mS/cm) in the root zone increased the concentration of
vitamin C in the tomato fruit.
Even if the varieties used in the previous studies are poorly known, it appears that
water shortage tends to increase fruit vitamin C content, as well as dry matter and soluble
solids content (°Brix).
6.2.4.3. Mineral nutrition
Effect of Nitrogen
A number of studies over more than the last 50 years are consistent to demonstrate that
increasing rates of nitrogen fertilizer tend to decrease the fruit vitamin C content.
According to Hamner et al.(1945) the influence of mineral nutrition on ascorbic acid
content has been found to be of relatively minor importance for different varieties, although
heavy application of nitrogen might cause some decrease; this decrease might be an indirect
effect since it might be associated with the influence of the nitrogen application in producing
greater foliage and resultant shading of the fruit on not pruned plants grown in the field in
rows 3 feet apart; in previous studies, no influence of nitrogen supply was found in plants
cultivated outside in sand pots 4 feet apart, with vines supported on poles, axillary growth
removed and thus evenly illuminated by direct sunshine.
For tomatoes grown in sand culture (cv. Bonny Best), nitrate supply for the month
prior the onset of ripening influenced fruit production and the ascorbic acid content of the